Renewable energy is collected from renewable sources such as sunlight, wind, rain, tides, waves and geothermal heat. Renewable energy is commonly used for generating electricity and for the heating or cooling of fluids.
Energy storage is the capture of energy for use at a later time. Acquiring energy for storage involves converting it to a storable form. An apparatus for storing energy may be referred to as an accumulator. Energy storage is an important aspect of renewable energy as the energy available is not regularly available when needed, nor needed when available. In one example, a passive solar heating system designed to produce sufficient heat for a living space in winter months continues to generate heat in summer months. In this example, the heat generated in the summer months is not needed to heat the living space and needs to be dispelled. This excess heat is commonly referred to as waste heat. Extracting waste heat energy and converting it to mechanical or electrical energy is a means of dispelling the waste heat while producing energy.
A working fluid is a pressurized gas or liquid that powers a machine. Examples include steam in a steam engine, air in a hot-air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder. In a thermodynamic system, the working fluid is a liquid or gas that absorbs or transmits energy.
A steam engine is a heat engine that uses the working fluid of steam to perform mechanical work. A steam engine is an external combustion engine wherein the working fluid is separate from the combustion product. Non-combustion heat sources such as solar energy, nuclear energy or geothermal energy may alternatively be used to create a working fluid.
The Rankine Cycle is a method that heats water to a high-pressure gas for purposes of converting a working fluid to mechanical energy. When the steam is expanded through at least one piston or turbine, the energy is transformed into mechanical work. Reduced-pressure fluid is exhausted to the atmosphere or condensed and returned to the boiler.
Conventionally, induction heating is the process of heating an electrically conducting object by electromagnetic induction, through heat generated in the object by eddy currents (also known as Foucault currents). An induction heater consists of an electromagnet and an electric oscillator that passes a high-frequency alternating current (AC) through the electromagnet, producing a rapidly alternating magnetic field. The rapidly alternating magnetic field is directed through a working coil toward the electrically conducting object, penetrating the electrically conducting object. This generates the electric eddy currents inside the electrically conducting object. The eddy currents flowing through the material encounter the material's resistance, resulting in joule heating of the material.
Joule heating, also known as ohmic or resistive heating, is the process by which the passage of an electric current through a conductor releases heat. The amount of heat released is proportional to the square of the current such that:H∝I2*R*t 
Where ‘H’ represents heat, ‘I’ represents current, ‘R’ represents resistance and ‘t’ represents time.
In ferromagnetic materials, heat may also be generated by magnetic hysteresis, in which the value of a physical property lags behind changes in the effect causing it, as for instance when magnetic induction lags behind the magnetizing force.
The frequency of current applied depends on the object size, material type, and coupling between a work coil and the depth of penetration.
A solenoid valve is an electromechanically operated valve that is controlled by an electric current through a solenoid. In a two-port solenoid valve, flow is switched on or off. Solenoid valves are most frequently used in fluidics for shutting off, releasing, dosing, distributing or mixing fluids. Solenoid valves are often employed for their rapid switching ability and high reliability.
An automatic bleeding valve or air-release valve (ARV) is a plumbing valve used to automatically release trapped air from a fluid system. Air trapped in a closed system can cause impede liquid flow or cause cavitation, reducing the system's efficacy and possibly causing a system to overheat. An ARV allows air to separate from fluid and exit the system.
A check valve, one-way valve or non-return valve allows fluid to flow in only one direction. Check valves are two-port valves, meaning they have two openings, one for fluid to enter and the other for fluid to exit. Check valves work automatically, needing no valve-handle operation.